After the near eradication of polio, Guillain-Barre syndrome (GBS) is the commonest cause of acute flaccid paralysis. GBS comprises a group of clinically and pathophysiologically related, acute monophasic neuropathic disorders of autoimmune origin. Despite the availability of two immunomodulatory therapies, a significant proportion of patients are left with permanent neurologic sequelae, including inability to walk unaided. Patients with neurologic sequelae almost always have failure of axon regeneration and target reinnervation. Anti-ganglioside antibodies (Abs) are the single most common autoimmune marker associated with GBS. The spectrum of pathobiologic effects of these Abs is not completely defined. We hypothesize that anti-ganglioside Abs with certain specificities act as inhibitory guidance cues by cross-linking gangliosides on growth cones of regenerating axons. Our goals are to examine the specificity of anti-ganglioside Ab- mediated inhibition (Aim 1), and to characterize the role of lipid rafts and ganglioside cross-linking (Aim 2), and secondary messengers (TNF receptor family members p75 and TROY and Rho GTPases) involved in this Ab-mediated inhibition of axon regeneration at the level of growth cones (Aims 3 and 4). We propose to use in vitro models of axon regeneration and growth cone behavior, and in a nerve graft animal model to study the pathobiologic effects of experimentally generated monoclonal anti-ganglioside Abs and compare them to anti-ganglioside Abs derived from GBS patients. These animal models will also be used to examine the role of ganglioside cross-linking, p75, and TROY and a downstream effector of RhoA GTPase. The proposed studies will provide proof of principle that anti-ganglioside Abs and their target gangliosides can induce inhibitory signals in regenerating axons and potentially identify targets for development of specific therapies. Our findings should provide insight into biology of failure of axon regeneration, which is relevant not only to peripheral neuropathies but also to CMS disorders like spinal cord injury and multiple sclerosis. Public information statement: This translational research project seeks to examine the potential mechanisms underlying permanent neurologic sequelae and incomplete recovery after Guillain-Barre syndrome and other neurologic disorders and to identify targets to develop rational therapeutic strategies to prevent this complication.